@article{TheysohnKraffEilersetal.2014, author = {Theysohn, Jens M. and Kraff, Oliver and Eilers, Kristina and Andrade, Dorian and Gerwig, Marcus and Timmann, Dagmar and Schmitt, Franz and Ladd, Mark E. and Ladd, Susanne C. and Bitz, Andreas}, title = {Vestibular effects of a 7 Tesla MRI examination compared to 1.5 T and 0 T in healthy volunteers}, series = {PLoS one}, volume = {9}, journal = {PLoS one}, number = {3}, publisher = {PLOS}, address = {San Francisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0092104}, pages = {e92104}, year = {2014}, abstract = {Ultra-high-field MRI (7 Tesla (T) and above) elicits more temporary side-effects compared to 1.5 T and 3 T, e.g. dizziness or "postural instability" even after exiting the scanner. The current study aims to assess quantitatively vestibular performance before and after exposure to different MRI scenarios at 7 T, 1.5 T and 0 T. Sway path and body axis rotation (Unterberger's stepping test) were quantitatively recorded in a total of 46 volunteers before, 2 minutes after, and 15 minutes after different exposure scenarios: 7 T head MRI (n = 27), 7 T no RF (n = 22), 7 T only B₀ (n = 20), 7 T in \& out B₀ (n = 20), 1.5 T no RF (n = 20), 0 T (n = 15). All exposure scenarios lasted 30 minutes except for brief one minute exposure in 7 T in \& out B₀. Both measures were documented utilizing a 3D ultrasound system. During sway path evaluation, the experiment was repeated with eyes both open and closed. Sway paths for all long-lasting 7 T scenarios (normal, no RF, only B₀) with eyes closed were significantly prolonged 2 minutes after exiting the scanner, normalizing after 15 minutes. Brief exposure to 7 T B₀ or 30 minutes exposure to 1.5 T or 0 T did not show significant changes. End positions after Unterberger's stepping test were significantly changed counter-clockwise after all 7 T scenarios, including the brief in \& out B₀ exposure. Shorter exposure resulted in a smaller alteration angle. In contrast to sway path, reversal of changes in body axis rotation was incomplete after 15 minutes. 1.5 T caused no rotational changes. The results show that exposure to the 7 Tesla static magnetic field causes only a temporary dysfunction or "over-compensation" of the vestibular system not measurable at 1.5 or 0 Tesla. Radiofrequency fields, gradient switching, and orthostatic dysregulation do not seem to play a role.}, language = {en} } @article{SchlamannYoonMaderwaldetal.2010, author = {Schlamann, Marc and Yoon, Min-Suk and Maderwald, Stefan and Pietrzyk, Thomas and Bitz, Andreas and Gerwig, Marcus and Forsting, Michael and Ladd, Susanne C. and Ladd, Mark E. and Kastrup, Oliver}, title = {Short term effects of magnetic resonance imaging on excitability of the motor cortex at 1.5T and 7T}, series = {Academic Radiology}, volume = {17}, journal = {Academic Radiology}, number = {3}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1076-6332}, doi = {10.1016/j.acra.2009.10.004}, pages = {277 -- 281}, year = {2010}, abstract = {Rationale and Objectives The increasing spread of high-field and ultra-high-field magnetic resonance imaging (MRI) scanners has encouraged new discussion of the safety aspects of MRI. Few studies have been published on possible cognitive effects of MRI examinations. The aim of this study was to examine whether changes are measurable after MRI examinations at 1.5 and 7 T by means of transcranial magnetic stimulation (TMS). Materials and Methods TMS was performed in 12 healthy, right-handed male volunteers. First the individual motor threshold was specified, and then the cortical silent period (SP) was measured. Subsequently, the volunteers were exposed to the 1.5-T MRI scanner for 63 minutes using standard sequences. The MRI examination was immediately followed by another TMS session. Fifteen minutes later, TMS was repeated. Four weeks later, the complete setting was repeated using a 7-T scanner. Control conditions included lying in the 1.5-T scanner for 63 minutes without scanning and lying in a separate room for 63 minutes. TMS was performed in the same way in each case. For statistical analysis, Wilcoxon's rank test was performed. Results Immediately after MRI exposure, the SP was highly significantly prolonged in all 12 subjects at 1.5 and 7 T. The motor threshold was significantly increased. Fifteen minutes after the examination, the measured value tended toward normal again. Control conditions revealed no significant differences. Conclusion MRI examinations lead to a transient and highly significant alteration in cortical excitability. This effect does not seem to depend on the strength of the static magnetic field.}, language = {en} } @article{UmutluKraffFischeretal.2013, author = {Umutlu, Lale and Kraff, Oliver and Fischer, Anja and Kinner, Sonja and Maderwald, Stefan and Nassenstein, Kai and Nensa, Felix and Gr{\"u}neisen, Johannes and Orzada, Stephan and Bitz, Andreas and Forsting, Michael and Ladd, Mark E. and Lauenstein, Thomas C.}, title = {Seven-Tesla MRI of the female pelvis}, series = {European Radiology}, volume = {23}, journal = {European Radiology}, number = {9}, publisher = {Springer}, address = {Berlin}, issn = {1432-1084}, doi = {10.1007/s00330-013-2868-0}, pages = {2364 -- 2373}, year = {2013}, language = {en} } @article{FiedlerLaddBitz2017, author = {Fiedler, Thomas M. and Ladd, Mark E. and Bitz, Andreas}, title = {SAR Simulations \& Safety}, series = {NeuroImage}, journal = {NeuroImage}, number = {Epub ahead of print}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1053-8119}, doi = {10.1016/j.neuroimage.2017.03.035}, year = {2017}, language = {en} } @article{FiedlerLaddClemensetal.2020, author = {Fiedler, Thomas M. and Ladd, Mark E. and Clemens, Markus and Bitz, Andreas}, title = {Safety of subjects during radiofrequency exposure in ultra-high-field magnetic resonance imaging}, series = {IEEE Letters on Electromagnetic Compatibility Practice and Applications}, volume = {2}, journal = {IEEE Letters on Electromagnetic Compatibility Practice and Applications}, number = {3}, publisher = {IEEE}, address = {New York, NY}, isbn = {2637-6423}, doi = {10.1109/LEMCPA.2020.3029747}, pages = {1 -- 8}, year = {2020}, abstract = {Magnetic resonance imaging (MRI) is one of the most important medical imaging techniques. Since the introduction of MRI in the mid-1980s, there has been a continuous trend toward higher static magnetic fields to obtain i.a. a higher signal-to-noise ratio. The step toward ultra-high-field (UHF) MRI at 7 Tesla and higher, however, creates several challenges regarding the homogeneity of the spin excitation RF transmit field and the RF exposure of the subject. In UHF MRI systems, the wavelength of the RF field is in the range of the diameter of the human body, which can result in inhomogeneous spin excitation and local SAR hotspots. To optimize the homogeneity in a region of interest, UHF MRI systems use parallel transmit systems with multiple transmit antennas and time-dependent modulation of the RF signal in the individual transmit channels. Furthermore, SAR increases with increasing field strength, while the SAR limits remain unchanged. Two different approaches to generate the RF transmit field in UHF systems using antenna arrays close and remote to the body are investigated in this letter. Achievable imaging performance is evaluated compared to typical clinical RF transmit systems at lower field strength. The evaluation has been performed under consideration of RF exposure based on local SAR and tissue temperature. Furthermore, results for thermal dose as an alternative RF exposure metric are presented.}, language = {en} } @inproceedings{BitzKobusScheenenetal.2013, author = {Bitz, Andreas and Kobus, Thiele and Scheenen, Tom W. J. and Ladd, Mark E.}, title = {RF Safety of the Combination of a 31P Tx/Rx Endorectal Coil \& a 1H Tx/Rx Body Array for 31P MRSI of the Prostate at 7T (311.)}, series = {20th Annual ISMRM scientific meeting and exhibition 2012 : Melbourne, Australia, 5 - 11 May 2012}, booktitle = {20th Annual ISMRM scientific meeting and exhibition 2012 : Melbourne, Australia, 5 - 11 May 2012}, number = {Volume 1}, publisher = {Curran}, address = {Red Hook, NY}, isbn = {978-1-62276-943-8}, issn = {1545-4428}, pages = {311}, year = {2013}, language = {en} } @article{FiedlerLaddBitz2017, author = {Fiedler, Thomas M. and Ladd, Mark E. and Bitz, Andreas}, title = {RF safety assessment of a bilateral four-channel transmit/receive 7 Tesla breast coil: SAR versus temperature limits}, series = {Medical Physics}, volume = {44}, journal = {Medical Physics}, number = {1}, doi = {10.1002/mp.12034}, pages = {143 -- 157}, year = {2017}, language = {en} } @article{OrzadaMaderwaldPoseretal.2010, author = {Orzada, Stephan and Maderwald, Stefan and Poser, Benedikt Andreas and Bitz, Andreas and Quick, Harald H. and Ladd, Mark E.}, title = {RF excitation using time interleaved acquisition of modes (TIAMO) to address B1 inhomogeneity in high-field MRI}, series = {Magnetic Resonance in Medicine}, volume = {64}, journal = {Magnetic Resonance in Medicine}, number = {2}, publisher = {Wiley-Liss}, address = {New York}, issn = {1522-2594}, doi = {10.1002/mrm.22527}, pages = {327 -- 333}, year = {2010}, abstract = {As the field strength and, therefore, the operational frequency in MRI is increased, the wavelength approaches the size of the human head/body, resulting in wave effects, which cause signal decreases and dropouts. Several multichannel approaches have been proposed to try to tackle these problems, including RF shimming, where each element in an array is driven by its own amplifier and modulated with a certain (constant) amplitude and phase relative to the other elements, and Transmit SENSE, where spatially tailored RF pulses are used. In this article, a relatively inexpensive and easy to use imaging scheme for 7 Tesla imaging is proposed to mitigate signal voids due to B1 field inhomogeneity. Two time-interleaved images are acquired using a different excitation mode for each. By forming virtual receive elements, both images are reconstructed together using GRAPPA to achieve a more homogeneous image, with only small SNR and SAR penalty in head and body imaging at 7 Tesla.}, language = {en} } @article{UmutluOrzadaKinneretal.2011, author = {Umutlu, Lale and Orzada, Stephan and Kinner, Sonja and Maderwald, Stefan and Bronte, Irina and Bitz, Andreas and Kraff, Oliver and Ladd, Susanne C. and Antoch, Gerald and Ladd, Mark E. and Quick, Harald H. and Lauenstein, Thomas C.}, title = {Renal imaging at 7 Tesla: preliminary results}, series = {European Radiology}, volume = {21}, journal = {European Radiology}, number = {4}, publisher = {Springer}, address = {Berlin}, issn = {1432-1084}, pages = {841 -- 849}, year = {2011}, abstract = {Objective To investigate the feasibility of 7T MR imaging of the kidneys utilising a custom-built 8-channel transmit/receive radiofrequency body coil. Methods In vivo unenhanced MR was performed in 8 healthy volunteers on a 7T whole-body MR system. After B0 shimming the following sequences were obtained: 1) 2D and 3D spoiled gradient-echo sequences (FLASH, VIBE), 2) T1-weighted 2D in and opposed phase 3) True-FISP imaging and 4) a T2-weighted turbo spin echo (TSE) sequence. Visual evaluation of the overall image quality was performed by two radiologists. Results Renal MRI at 7T was feasible in all eight subjects. Best image quality was found using T1-weighted gradient echo MRI, providing high anatomical details and excellent conspicuity of the non-enhanced vasculature. With successful shimming, B1 signal voids could be effectively reduced and/or shifted out of the region of interest in most sequence types. However, T2-weighted TSE imaging remained challenging and strongly impaired because of signal heterogeneities in three volunteers. Conclusion The results demonstrate the feasibility and diagnostic potential of dedicated 7T renal imaging. Further optimisation of imaging sequences and dedicated RF coil concepts are expected to improve the acquisition quality and ultimately provide high clinical diagnostic value.}, language = {en} } @article{NoureddineKraffLaddetal.2019, author = {Noureddine, Yacine and Kraff, Oliver and Ladd, Mark E. and Wrede, Karsten and Chen, Bixia and Quick, Harald H. and Schaefers, Georg and Bitz, Andreas}, title = {Radiofrequency induced heating around aneurysm clips using a generic birdcage head coil at 7 Tesla under consideration of the minimum distance to decouple multiple aneurysm clips}, series = {Magnetic Resonance in Medicine}, journal = {Magnetic Resonance in Medicine}, number = {Early view}, publisher = {Wiley}, address = {Weinheim}, issn = {1522-2594}, doi = {10.1002/mrm.27835}, pages = {1 -- 17}, year = {2019}, language = {en} } @article{FiedlerOrzadaFloeseretal.2022, author = {Fiedler, Thomas M. and Orzada, Stephan and Fl{\"o}ser, Martina and Rietsch, Stefan H. G. and Schmidt, Simon and Stelter, Jonathan K. and Wittrich, Marco and Quick, Harald H. and Bitz, Andreas and Ladd, Mark E.}, title = {Performance and safety assessment of an integrated transmitarray for body imaging at 7 T under consideration of specificabsorption rate, tissue temperature, and thermal dose}, series = {NMR in Biomedicine}, volume = {35}, journal = {NMR in Biomedicine}, number = {5}, publisher = {Wiley}, issn = {0952-3480 (Print)}, doi = {10.1002/nbm.4656}, pages = {1 -- 17}, year = {2022}, abstract = {In this study, the performance of an integrated body-imaging array for 7 T with 32 radiofrequency (RF) channels under consideration of local specific absorption rate (SAR), tissue temperature, and thermal dose limits was evaluated and the imaging performance was compared with a clinical 3 T body coil. Thirty-two transmit elements were placed in three rings between the bore liner and RF shield of the gradient coil. Slice-selective RF pulse optimizations for B1 shimming and spokes were performed for differently oriented slices in the body under consideration of realistic constraints for power and local SAR. To improve the B1+ homogeneity, safety assessments based on temperature and thermal dose were performed to possibly allow for higher input power for the pulse optimization than permissible with SAR limits. The results showed that using two spokes, the 7 T array outperformed the 3 T birdcage in all the considered regions of interest. However, a significantly higher SAR or lower duty cycle at 7 T is necessary in some cases to achieve similar B1+ homogeneity as at 3 T. The homogeneity in up to 50 cm-long coronal slices can particularly benefit from the high RF shim performance provided by the 32 RF channels. The thermal dose approach increases the allowable input power and the corresponding local SAR, in one example up to 100 W/kg, without limiting the exposure time necessary for an MR examination. In conclusion, the integrated antenna array at 7 T enables a clinical workflow for body imaging and comparable imaging performance to a conventional 3 T clinical body coil.}, language = {en} } @article{OrzadaBitzSchaeferetal.2011, author = {Orzada, Stephan and Bitz, Andreas and Sch{\"a}fer, Lena C. and Ladd, Susanne C. and Ladd, Mark E. and Maderwald, Stefan}, title = {Open design eight-channel transmit/receive coil for high-resolution and real-time ankle imaging at 7 T}, series = {Medical Physics}, volume = {38}, journal = {Medical Physics}, number = {3}, publisher = {Wiley}, address = {Hoboken}, issn = {2473-4209}, doi = {10.1118/1.3553399}, pages = {1162 -- 1167}, year = {2011}, abstract = {Purpose: At 1.5 T, real-time MRI of joint movement has been shown to be feasible. However, 7 T, provides higher SNR and thus an improved potential for parallel imaging acceleration. The purpose of this work was to build an open, U-shaped eight-channel transmit/receive microstrip coil for 7 T MRI to enable high-resolution and real-time imaging of the moving ankle joint. Methods: A U-shaped eight-channel transmit/receive array for the human ankle was built.urn:x-wiley:00942405:mp3399:equation:mp3399-math-0001-parameters and urn:x-wiley:00942405:mp3399:equation:mp3399-math-0002-factor were measured. SAR calculations of different ankle postures were performed to ensure patient safety. Inhomogeneities in the transmit field consequent to the open design were compensated for by the use of static RF shimming. High-resolution and real-time imaging was performed in human volunteers. Results: The presented array showed good performance with regard to patient comfort and image quality. High acceleration factors of up to 4 are feasible without visible acceleration artifacts. Reasonable image homogeneity was achieved with RF shimming. Conclusions: Open, noncylindrical designs for transmit/receive coils are practical at 7 T and real-time imaging of the moving joint is feasible with the presented coil design.}, language = {en} } @article{KraffWredeSchoembergetal.2013, author = {Kraff, Oliver and Wrede, Karsten H. and Schoemberg, Tobias and Dammann, Philipp and Noureddine, Yacine and Orzada, Stephan and Ladd, Mark E. and Bitz, Andreas}, title = {MR safety assessment of potential RF heating from cranial fixation plates at 7 T}, series = {Medical Physics}, volume = {40}, journal = {Medical Physics}, number = {4}, publisher = {Wiley}, address = {Hoboken}, issn = {2473-4209}, doi = {10.1118/1.4795347}, pages = {042302-1 -- 042302-10}, year = {2013}, language = {en} } @article{OrzadaJohstMaderwaldetal.2013, author = {Orzada, Stephan and Johst, S{\"o}ren and Maderwald, Stefan and Bitz, Andreas and Solbach, Klaus and Ladd, Mark E.}, title = {Mitigation of B1(+) inhomogeneity on single-channel transmit systems with TIAMO}, series = {Magnetic Resonance in Medicine}, volume = {70}, journal = {Magnetic Resonance in Medicine}, number = {1}, publisher = {Wiley}, address = {Weinheim}, issn = {1522-2594}, doi = {10.1002/mrm.24453}, pages = {290 -- 294}, year = {2013}, language = {en} } @article{OrzadaFiedlerBitzetal.2020, author = {Orzada, Stephan and Fiedler, Thomas M. and Bitz, Andreas and Ladd, Mark E. and Quick, Harald H.}, title = {Local SAR compression with overestimation control to reduce maximum relative SAR overestimation and improve multi-channel RF array performance}, series = {Magnetic Resonance Materials in Physics, Biology and Medicine}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, number = {34 (2021)}, publisher = {Springer}, address = {Heidelberg}, isbn = {1352-8661}, doi = {10.1007/s10334-020-00890-0}, pages = {153 -- 164}, year = {2020}, abstract = {Objective In local SAR compression algorithms, the overestimation is generally not linearly dependent on actual local SAR. This can lead to large relative overestimation at low actual SAR values, unnecessarily constraining transmit array performance. Method Two strategies are proposed to reduce maximum relative overestimation for a given number of VOPs. The first strategy uses an overestimation matrix that roughly approximates actual local SAR; the second strategy uses a small set of pre-calculated VOPs as the overestimation term for the compression. Result Comparison with a previous method shows that for a given maximum relative overestimation the number of VOPs can be reduced by around 20\% at the cost of a higher absolute overestimation at high actual local SAR values. Conclusion The proposed strategies outperform a previously published strategy and can improve the SAR compression where maximum relative overestimation constrains the performance of parallel transmission.}, language = {en} } @article{NoureddineKraffLaddetal.2017, author = {Noureddine, Yacine and Kraff, Oliver and Ladd, Mark E. and Wrede, Karsten H. and Chen, Bixia and Quick, Harald H. and Schaefers, Gregor and Bitz, Andreas}, title = {In vitro and in silico assessment of RF-induced heating around intracranial aneurysm clips at 7 Tesla}, series = {Magnetic Resonance in Medicine}, journal = {Magnetic Resonance in Medicine}, number = {Early view}, publisher = {Wiley}, address = {Weinheim}, issn = {1522-2594}, doi = {10.1002/mrm.26650}, pages = {14 Seiten}, year = {2017}, language = {en} } @article{MaasVosLagemaatetal.2014, author = {Maas, Marnix C. and Vos, Eline K. and Lagemaat, Miriam W. and Bitz, Andreas and Orzada, Stephan and Kobus, Thiele and Kraff, Oliver and Maderwald, Stefan and Ladd, Mark E. and Scheenen, Tom W. J.}, title = {Feasibility of T₂-weighted turbo spin echo imaging of the human prostate at 7 tesla}, series = {Magnetic Resonance in Medicine}, volume = {71}, journal = {Magnetic Resonance in Medicine}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1522-2594}, doi = {10.1002/mrm.24818}, pages = {1711 -- 1719}, year = {2014}, abstract = {Purpose To demonstrate that high quality T₂-weighted (T2w) turbo spin-echo (TSE) imaging of the complete prostate can be achieved routinely and within safety limits at 7 T, using an external transceive body array coil only. Methods Nine healthy volunteers and 12 prostate cancer patients were scanned on a 7 T whole-body system. Preparation consisted of B₀ and radiofrequency shimming and localized flip angle calibration. T₁ and T₂ relaxation times were measured and used to define the T2w-TSE protocol. T2w imaging was performed using a TSE sequence (pulse repetition time/echo time 3000-3640/71 ms) with prolonged excitation and refocusing pulses to reduce specific absorption rate. Results High quality T2w TSE imaging was performed in less than 2 min in all subjects. Tumors of patients with gold-standard tumor localization (MR-guided biopsy or prostatectomy) were well visualized on 7 T imaging (n = 3). The number of consecutive slices achievable within a 10-g averaged specific absorption rate limit of 10 W/kg was ≥28 in all subjects, sufficient for full prostate coverage with 3-mm slices in at least one direction. Conclusion High quality T2w TSE prostate imaging can be performed routinely and within specific absorption rate limits at 7 T with an external transceive body array.}, language = {en} } @article{SchlamannVoigtMaderwaldetal.2010, author = {Schlamann, Marc and Voigt, Melanie A. and Maderwald, Stefan and Bitz, Andreas and Kraff, Oliver and Ladd, Susanne C. and Ladd, Mark E. and Forsting, Michael and Wilhelm, Hans}, title = {Exposure to high-field MRI does not affect cognitive function}, series = {Journal of Magnetic Resonance Imaging}, volume = {31}, journal = {Journal of Magnetic Resonance Imaging}, number = {5}, publisher = {Wiley-Liss}, address = {New York}, issn = {1522-2586}, doi = {10.1002/jmri.22065}, pages = {1061 -- 1066}, year = {2010}, abstract = {Purpose To assess potential cognitive deficits under the influence of static magnetic fields at various field strengths some studies already exist. These studies were not focused on attention as the most vulnerable cognitive function. Additionally, mostly no magnetic resonance imaging (MRI) sequences were performed. Materials and Methods In all, 25 right-handed men were enrolled in this study. All subjects underwent one MRI examination of 63 minutes at 1.5 T and one at 7 T within an interval of 10 to 30 days. The order of the examinations was randomized. Subjects were referred to six standardized neuropsychological tests strictly focused on attention immediately before and after each MRI examination. Differences in neuropsychological variables between the timepoints before and after each MRI examination were assessed and P-values were calculated Results Only six subtests revealed significant differences between pre- and post-MRI. In these tests the subjects achieved better results in post-MRI testing than in pre-MRI testing (P = 0.013-0.032). The other tests revealed no significant results. Conclusion The improvement in post-MRI testing is only explicable as a result of learning effects. MRI examinations, even in ultrahigh-field scanners, do not seem to have any persisting influence on the attention networks of human cognition immediately after exposure.}, language = {en} } @article{NoureddineBitzLaddetal.2015, author = {Noureddine, Yacine and Bitz, Andreas and Ladd, Mark E. and Th{\"u}rling, Markus and Ladd, Susanne C. and Schaefers, Gregor and Kraff, Oliver}, title = {Experience with magnetic resonance imaging of human subjects with passive implants and tattoos at 7 T: a retrospective study}, series = {Magnetic Resonance Materials in Physics, Biology and Medicine}, volume = {28}, journal = {Magnetic Resonance Materials in Physics, Biology and Medicine}, number = {6}, publisher = {Springer}, address = {Berlin}, issn = {1352-8661}, doi = {10.1007/s10334-015-0499-y}, pages = {577 -- 590}, year = {2015}, language = {en} } @article{RietschBrunheimOrzadaetal.2019, author = {Rietsch, Stefan H. G. and Brunheim, Sascha and Orzada, Stephan and Voelker, Maximilian N. and Maderwald, Stefan and Bitz, Andreas and Gratz, Marcel and Ladd, Mark E. and Quick, Harald H.}, title = {Development and evaluation of a 16-channel receive-only RF coil to improve 7T ultra-high field body MRI with focus on the spine}, series = {Magnetic Resonance in Medicine}, journal = {Magnetic Resonance in Medicine}, number = {Early view}, publisher = {Wiley}, address = {Weinheim}, issn = {1522-2594}, doi = {10.1002/mrm.27731}, year = {2019}, language = {en} }